Radio network controller peer-to-peer exchange of user equipment measurement information

ABSTRACT

A drifting wireless transmit/receive unit (WTRU) has an associated drift radio network controller (D-RNC) and an associated servicing radio network controller (S-RNC). The D-RNC sends a request message to the S-RNC requesting measurements of the drifting WTRU. The S-RNC receives the request message and sends an information message with the requested measurements to the D-RNC. The D-RNC receives the information message.

CROSS REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims priority from U.S. provisionalapplication No. 60/392,122, filed Jun. 27, 2002, which is incorporatedby reference as if fully set forth.

FIELD OF INVENTION

[0002] This invention relates to wireless communication systems. Inparticular, the invention relates to the transfer of information betweenradio network controllers in such systems.

BACKGROUND

[0003]FIG. 1 is an illustration of a wireless communication system whereall the users are handled by a radio network controller (RNC) 20. Eachuser, wireless transmit/receive unit (WTRU) 24, wirelessly communicateswith a Node-B 22 ₁. A group of Node-Bs 22 ₁-22 ₂ are controlled by theradio network controller (RNC) 20.

[0004] As the WTRU 24 moves, the WTRU 24 ₁, 24 ₂ is handed off betweenbase stations/Node-Bs 32, 34. FIG. 2 is an illustration of a WTRU 24 ₁,24 ₂ moving from an area handled by a first RNC 28 to an area handled bya second RNC 26. The WTRU 24 ₂ is considered to have “drifted” into thenew RNC's region and that RNC (the second RNC) is considered the driftRNC (D-RNC) 26. The D-RNC 26 has Node-Bs 32, which it controls. Thefirst RNC is referred to as the servicing RNC (S-RNC) 28. Typically, theRNCs (S-RNC 28 and D-RNC 26) can communicate some information to eachother over a RNC interface (Iur). After the WTRU 24 ₂ “drifts” to theD-RNC 26, the D-RNC 26 performs functions, such as dynamic channelallocation (DCA), admission control, scheduling and RRM functions forthe “drifting” WTRU 24 ₂. The S-RNC 28 still performs other functionsfor the “drifting” WTRU 24 ₂, such as handoff decisions and collectingof WTRU downlink measurements. When the WTRU 24 has not “drifted”, suchas in FIG. 1, the RNC 20 handling the WTRU 24 performs the functions ofboth the S-RNC 28 and D-RNC 26.

[0005] Under the R99, R4 and R5 Iur specifications as proposed for thethird generation partnership project (3GPP), when the WTRU 24 ₁, 24 ₂ ishanded over from the S-RNC 28 to the D-RNC 26, cell loading and manyNode-B measurements are sent from the S-RNC 28 to the D-RNC 26. However,there is no mechanism to transfer certain information from the S-RNC 28to the D-RNC 26, such as the WTRU measurements.

[0006] Accordingly, it is desirable to have better peer-to-peercommunications between RNCs.

SUMMARY

[0007] A drifting wireless transmit/receive unit (WTRU) has anassociated drift radio network controller (D-RNC) and an associatedservicing radio network controller (S-RNC). The D-RNC sends a requestmessage to the S-RNC requesting measurements of the drifting WTRU. TheS-RNC receives the request message and sends an information message withthe requested measurements to the D-RNC. The D-RNC receives theinformation message.

BRIEF DESCRIPTION OF THE DRAWING(S)

[0008]FIG. 1 is an illustration of a RNC handling a WTRU.

[0009]FIG. 2 is an illustration of a WTRU drifting between RNCs.

[0010]FIG. 3 is a block diagram of a preferred embodiment forpeer-to-peer information exchange.

[0011]FIG. 4 is a flow chart of a preferred embodiment for peer-to-peerinformation exchange.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0012] Although the preferred embodiments are described in conjunctionwith a third generation partnership program (3GPP) wideband codedivision multiple access (W-CDMA) system, the embodiments are applicableto other wireless communication systems.

[0013] Hereafter, a wireless transmit/receive unit (WTRU) includes butis not limited to a user equipment, mobile station, fixed or mobilesubscriber unit, pager, or any other type of device capable of operatingin a wireless environment.

[0014]FIG. 3 is a simplified block diagram of a S-RNC 40, a D-RNC 38 andan IUR 36 for a “drifting” WTRU 24 ₂ using peer-to-peer informationexchange. FIG. 4 is a flow chart of peer-to-peer information exchange.The S-RNC 40 typically performs functions such as handoff decisions andcollecting of WTRU downlink measurements for the “drifting” WTRU 24 ₂.The D-RNC 38 typically performs functions such as DCA, admissioncontrol, scheduling and RRM functions for the “drifting” WTRU 24 ₂.

[0015] The D-RNC 38 has a RRM 42. The RRM 42 controls the resources forthe WTRUs of cells associated with the D-RNC 38. The D-RNC 38 collectsuplink measurements for the cell of the “drifting” WTRU 24 ₂ as well asother cells using an uplink measurement collection device 44. Thesemeasurements are available to the RRM 42 for use in resource allocationand management. The RRM 42 also has information for WTRUs that it isperforming S-RNC functions.

[0016] The D-RNC 38 has logic associated with the RRM 42. When the RRM42 requires downlink measurements of the “drifting” WTRU 242 or a groupor WTRUs, the logic 46 initiates a WTRU measurement request device 48 tosend a message through the Iur 36 for such information, step 60.

[0017] Examples of the information that may be requested by the D-RNC38, include downlink common control physical channel (CCPCH) receivedsignal code power (RSCP), interference signal code power (ISCP)measurements and/or traffic volume measurements. Preferably, the D-RNCinformation request messages can not request the WTRU 24 ₂ to make andsend measurements, but the D-RNC 38 requests such measurementinformation currently available at the S-RNC 40.

[0018] The signaling messages on the Iur 36 allows any D-RNC 38 toinitiate information exchange with S-RNCs on an individual WTRU, groupsof WTRUs or WTRUs present in one or more cells for which it does notassume itself the role of an S-RNC. This procedure is preferably not asimple “forwarding” of WTRU-specific information, such as WTRUmeasurements. Preferably, the D-RNC logic 46 generally makes thedecision of the type of information to request, although the logicfunction 46 may be performed by the controlling RNC (C-RNC). A logicfunction 46 in the D-RNC 38 decides if and when it will requestmeasurements to be forwarded from the S-RNC 40. For example, if theD-RNC 38 detects that more than a threshold number or percentage, suchas 10%, of its WTRUs are in “drift” mode, it would typically startrequesting measurements to be forwarded. In the preferredimplementation, existing information elements and standardized WTRUmeasurements/reporting mechanisms defined by the 3GPP standard forNode-B interface (Iub)/Iur are utilized.

[0019] One preferred message allows the D-RNC 38 to request measurementsfor a particular “drift” WTRU 24 ₂ for a given time frame or for all the“drift” WTRUs in a given cell or group of cells associated with theS-RNC 40 for a given time frame. One scenario that requesting a group ofWTRUs information is desirable is when many WTRUs having a particularS-RNC are in “drift” mode. For example, a first train station issupported by a first RNC and a second train station by a second RNC. Allof the WTRUs boarding a train starting at the first station anddeparting at the second station may have the first RNC as the S-RNC 40and the second RNC as the D-RNC 38. In this scenario, requesting WTRUinformation for the group of “drifting” WTRUs reduces the messagingoverhead. However, a scenario where the procedure allows only a singleWTRU per message may be used, with increased messaging overhead.

[0020] The message is received by the “drifting” WTRU's S-RNC 40, step62. That S-RNC 40 has a WTRU measurement collection device 52. The WTRUmeasurement collection device 52 stores the particular WTRU's downlinkmeasurements. A WTRU measurement response device 50 sends ameasurement/information message to the D-RNC 38 through the Iur 36, step64. The D-RNC RRM 42 uses these measurements in its resource allocationsand management, step 66. One benefit of transferring such data throughthe IUR 36 is such data transfer is typically quite fast.

[0021] One preferred approach for requesting and transferring the WTRUmeasurements uses the radio network sublayer application part (RNSAP)procedures. RNSAP has four basic modules. One of these modules is the“Global Procedures” module. That module contains procedures that involvesignaling for exchange of cell level information between RNCs. Forexample, received total wide band power, load and global positioningsystem (GPS) timing information is exchanged using the CommonMeasurement messages.

[0022] The list of information exchanged using RNSAP Global Proceduresis expanded to allow for better RRM. In particular, this informationaids primarily handover decisions. For example, information associatedwith cell biasing of handovers to neighboring RNCs would aid in suchdecisions. In the proposed 3GPP system, the information exchanged usingthe Global Procedures module is not related to a particular WTRU orgroup of WTRUs. As a result, it does not support the transfer of WTRUdata transfer across the Iur 36. Preferably, information shouldtransferred across the Iur 36 using RNSAP procedures, if the analogouscell information is available in the S-RNC 40 for relevant RRM decisionsby the D-RNC 38.

[0023] Such information exchange over the Iur 36 allows a D-RNC 38 torequest WTRU measurement information from the S-RNC 40 and allows morecell information to be exchanged between peer RNCs using the RNSAPGlobal Procedures module. Typically, this exchange of informationenhances the performance of RRM algorithms (DCA, Admission Control,Scheduling and others) in the D-RNC 38, due to the availability of WTRUmeasurements. Enhanced RRM, especially DCA, facilitates performance,efficiency and robustness in wireless systems, such as the time divisionduplex (TDD) mode of 3GPP.

What is claimed is:
 1. A method for exchanging information between a drift radio network controller (D-RNC) and a servicing radio network controller (S-RNC) of at least one drifting wireless transmit/receive unit (WTRU), the method comprising: the D-RNC sending a request message to the S-RNC requesting measurements of the drifting WTRU; the S-RNC receiving the request message and sending an information message with the requested measurements to the D-RNC; and the D-RNC receiving the information message.
 2. The method of claim 1 wherein the requested measurements include a downlink common control physical channel (CCPCH) received signal code power (RSCP).
 3. The method of claim 1 wherein the requested measurements include an interference signal code power (ISCP) measurement.
 4. The method of claim 1 wherein the requested measurements include traffic volume measurements.
 5. The method of claim 1 wherein the requested measurements include other WTRU known measurements.
 6. The method of claim 1 wherein the request message and the information message is sent through a radio network controller interface (Iur).
 7. The method of claim 1 wherein the requested measurements are available at the S-RNC without requesting the drifting RNC to make measurements.
 8. The method of claim 1 wherein the request message is for a single drifting WTRU.
 9. The method of claim 1 wherein the request message is for a group of drifting WTRUs.
 10. The method of claim 1 wherein the request message is sent after a threshold number of WTRUs of the D-RNC are in drift mode.
 11. The method of claim 1 wherein the request message is sent after a threshold percentage of WTRUs of the D-RNC are in drift mode.
 12. The method of claim 1 wherein the information message is sent using radio network sublayer application part procedures.
 13. A wireless communication system comprising: a drifting wireless transmit/receive unit (WTRU), a drifting radio network controller (D-RNC) and a servicing radio network controller (S-RNC) associated with the drifting WTRU; the D-RNC comprising: an uplink measurement collection device for collecting uplink measurements of cells associated with the D-RNC; a WTRU measurement request device for sending a message requesting measurements of the drifting WTRU; and a radio resource management device for managing radio resources of the D-RNC, the radio resource management device receiving the collected uplink measurements and the drifting WTRU measurements; and the S-RNC comprising: a WTRU measurement collection device for collecting measurements of the WTRU; and a WTRU measurement response device for sending collected measurements of the WTRU to the D-RNC in response to receiving the sent message.
 14. The system of claim 13 further comprises logic for determining when to request the drifting WTRU measurements.
 15. The system of claim 14 wherein the D-RNC comprises the logic.
 16. The system of claim 14 wherein a controlling radio network controller comprises the logic.
 17. The system of claim 13 further comprises a radio network controller interface (Iur), wherein the sent collected measurements and the sent requesting measurement message are sent through the Iur.
 18. The system of claim 17 wherein the sent collected measurements and the sent requesting measurement message are sent using radio network sublayer application part procedures.
 19. A radio network controller (RNC) for controlling wireless users, the RNC capable of operating as a drift RNC (D-RNC) and as a servicing RNC (S-RNC), the RNC comprising: an uplink measurement collection device for collecting uplink measurements of cells associated with the RNC; a wireless transmit/receive unit (WTRU) measurement request device for sending a message requesting measurements of a drifting WTRU; a radio resource management device for managing radio resources of the RNC, the radio resource management device receiving the collected uplink measurements and the drifting WTRU measurements; a WTRU measurement collection device for collecting measurements of the WTRU; and a WTRU measurement response device for sending collected measurements of the WTRU to another RNC in response to receiving a WTRU measurement request message
 20. The RNC of claim 19 further comprising logic for determining when to request the drifting WTRU measurements.
 21. The RNC of claim 19 wherein the WTRU measurement request device and the WTRU measurement response device use radio network sublayer application part procedures for signaling.
 22. A radio network controller (RNC) for controlling wireless users, the RNC capable of operating as a drift RNC (D-RNC) and as a servicing RNC (S-RNC), the RNC comprising: means for collecting uplink measurements of cells associated with the RNC; means for sending a message requesting measurements of a drifting wireless transmit/receive unit (WTRU); means for managing radio resources of the RNC, the radio resource management device receiving the collected uplink measurements and the drifting WTRU measurements; means for collecting measurements of the WTRU; and means for sending collected measurements of the WTRU to another RNC in response to receiving a WTRU measurement request message
 23. The RNC of claim 22 further comprising logic means for determining when to request the drifting WTRU measurements.
 24. The RNC of claim 22 wherein the means for sending a message requesting WTRU measurements and the means for sending collected measurements use radio network sublayer application part procedures for signaling. 